Grid Circle Analyzer - Computer Aided Measurement of Deformation

The grid circle method of measuring strain in a sheet metal stamping is necessary for understanding formability. However, this method has primarily been limited to use as a research tool because of the slow, tedious measurements required to measure strain from each deformed circle. An automatic method of measuring strains has been developed which combines a solid state camera with a minicomputer to calculate a best fit ellipse through each deformed circle. The computer calculates and prints the major and minor strain. The accuracy of this automatic system is comparable to measurements made from a toolmaker's microscope and is ∼3 times faster. Furthermore, it is not necessary to first section large stampings to read strains. These advantages give this new method the ability to rapidly read strains at the press shop to aid in implementing technological advances.